1. Field of the Invention
The present invention relates to a patterning process using self-assembly.
2. Description of the Related Art
In 1980s, photo-exposure using a g-beam (436 nm) or an i-beam (365 nm) of a mercury lamp as a light source had been widely used in the resist patterning. As a means for further miniaturization, shifting to a shorter wavelength of the exposure light was assumed to be effective, so that, in mass production process after the DRAM (Dynamic Random Access Memory) with 64 megabits (processing dimension of 0.25 μm or less) in 1990s, a KrF excimer laser (248 nm), a shorter wavelength than the i-beam (365 nm), had been used in place of the i-beam as an exposure light source. However, in production of DRAMs with integration of 256 MB and 1 GB or higher which require further miniaturized process technologies (processing dimension of 0.2 μm or less), a light source with further short wavelength is required, and thus, a photolithography using an ArF excimer laser (193 nm) has been investigated seriously since about a decade ago. At first, the ArF lithography was planned to be applied to manufacturing of a device starting from a 180-nm node device, but the life of the KrF excimer lithography was prolonged to mass production of the 130-nm node device; and thus, a full-fledged application of the ArF lithography started from the 90-nm node. Further, mass production of the 65-nm node device is now underway by combining thereof with a lens having an increased NA till 0.9. Further shortening of wavelength of the exposure light is progressing in the next 45-nm node device; and for that, the F2-lithography with 157 nm wavelength became a candidate. However, there are many problems with the F2 lithography: cost-up of a scanner due to use of a large quantities of expensive CaF2 single crystals for a projection lens; extremely poor sustainability of a soft pellicle, which leads to change of an optical system due to introduction of a hard pellicle; decrease in etching resistance of a photoresist film, and so forth. Because of these problems, development of the F2 lithography was suspended, and the ArF immersion lithography was introduced.
In the ArF immersion lithography, water having refractive index of 1.44 is introduced between a projection lens and a wafer by a partial fill method thereby enabling high speed scanning; and thus, mass production of the 45-nm node device is now underway by using a lens with a NA class of 1.3.
For the 32-nm node lithography technology, a lithography with an extreme ultraviolet beam (EUV) of 13.5 nm wavelength is considered to be a candidate. Problems to be solved in the EUV lithography are to obtain a higher output power of the laser, a higher sensitivity of the photoresist film, a higher resolution power, a lower line edge roughness (LER), a non-defect MoSi laminate mask, a lower aberration of the reflective mirror, and so forth; and thus, there are mounting problems to be solved.
Development of the immersion lithography with a high refractive index, another candidate for the 32-nm node, was suspended, because transmittance of LUAG, a candidate for a high refractive index lens, is low, and refractive index of the liquid could not reach an aimed value of 1.8.
As mentioned above, in the photo-exposure used as a general technology, resolution power based on the wavelength of a light source is approaching to its inherent limit. Therefore, in recent years, development by an organic solvent, with which a very fine hole pattern that could not be achieved by a patterning process with a positive tone by a conventional alkaline development is formed by a patterning process with a negative tone by the organic solvent development, is receiving an attention again. This is a patterning process with which a negative pattern is formed by the organic solvent development by using a positive photoresist composition having a high resolution power. Further, an investigation to obtain a doubled resolution power by combining two developments of the alkaline development and the organic solvent development is now underway. However, under the present situation, patterning to form a fine pattern by a lithography with 30 nm or less, especially by a lithography with 10 nm or less is difficult.
In recent years, a pattern having a regularity could be successively obtained by using a self-assembling technology of a block copolymer without using a lithography process (For example, Patent Documents 1 to 3). In addition, patterning of about 30 nm by a combination with the ArF immersion lithography was reported (Non-Patent Document 1).
However, the pattern obtained by these self-assembly materials has many problems in uniformity and regularity of the pattern form even though the pattern thereof is about 30 nm in its size, so that this has not been realized as a practical method; and thus, these problems are required to be solved.